The present invention relates to the cultivation of trees, such as coniferous trees, and to methods of pruning the roots of tree seedlings.
The demand for trees, such as coniferous trees, to provide lumber for making wood products continues to increase. There is therefore a need for methods that improve the growth rate of commercially desirable trees, so that the time from planting to harvest of the tree is reduced. The present inventors have discovered methods of pruning tree seedling roots that stimulate an unexpectedly high level of root growth. Enhanced root growth also promotes growth of the whole seedling, thereby improving the efficiency of commercial tree culture.
In accordance with the foregoing, in one aspect the present invention provides methods for pruning the roots of tree seedlings. The methods of this aspect of the invention include: (a) a first root pruning step wherein the roots of a majority of members of a population of tree seedlings are laterally pruned; and (b) a second root pruning step, that occurs after the first root pruning step, wherein the roots of the majority of members of the population of tree seedlings are again laterally pruned. In the practice of the methods of this aspect of the invention, the population of tree seedlings is arranged as at least two adjacent pairs of rows (hereinafter referred to as xe2x80x9crow pairsxe2x80x9d) of seedlings, and the roots of the majority of the seedlings are pruned shorter during the first pruning step than during the second pruning step. In some embodiments of the invention, the population of tree seedlings is arranged as six adjacent row pairs of seedlings. In some embodiment of the methods of the invention, a multiplicity of Coulter discs (hereinafter referred to as Coulters) are used to prune the seedling roots. Typically the second root pruning steps takes place within six months of the first root pruning step. For example, the first root pruning step can occur in July and the second root pruning step can occur in December of the same year.
In one embodiment, the present invention provides methods for pruning the roots of a population of tree seedlings wherein: (a) the population of tree seedlings comprises a first row pair, a second row pair, a third row pair, a fourth row pair, a fifth row pair, and a sixth row pair; (b) a first adjacent area is adjacent to the first row pair, and external to the population of tree seedlings; (c) a second adjacent area is adjacent to the sixth row pair, and external to the population of tree seedlings; (d) a first inter-row space is defined by the first row pair and the second row pair, a second inter-row space is defined by the second row pair and the third row pair, a third inter-row space is defined by the third row pair and the fourth row pair, a fourth inter-row space is defined by the fourth row pair and the fifth row pair, and a fifth inter-row space is defined by the fifth row pair and the sixth row pair; (e) the first pruning step utilizes a first Coulter, a second Coulter, a third Coulter, a fourth Coulter, a fifth Coulter, a sixth Coulter, a seventh Coulter, an eighth Coulter, and a ninth Coulter, wherein the first Coulter prunes roots in the first adjacent area, the second Coulter prunes roots in the first inter-row space, the third and fourth Coulters prune roots in the second inter-row space, the fifth Coulter prunes roots in the third inter-row space, the sixth and seventh Coulters prune roots in the fourth inter-row space, the eighth Coulter prunes roots in the fifth inter-row space, and the ninth Coulter prunes roots in the second adjacent area; and (f) the second pruning step utilizes a tenth Coulter, an eleventh Coulter, a twelfth Coulter, and a thirteenth Coulter, wherein the tenth Coulter prunes roots in the first adjacent area, the eleventh Coulter prunes roots in the second inter-row space, the twelfth Coulter prunes roots in the fourth inter-row space, and the thirteenth Coulter prunes roots in the second adjacent area.
The methods of the invention promote tree seedling root growth, thereby promoting the growth and development of the seedlings. The methods of the invention are useful in any situation in which it is desired to prune the roots of tree seedlings. For example, the methods of the invention are useful for pruning the roots of coniferous tree seedlings, thereby promoting the growth of a fibrous root system which, in turn, promotes the survival and growth of the whole seedling upon transplantation or outplanting to a new growth environment.